1598
C. Santos et al. / Bioorg. Med. Chem. Lett. 15 (2005) 1595–1598
than 7.4. Quite importantly, the in vivo results suggest
that hepatotoxicity of paracetamol can be efficiently re-
duced by an appropriate choice of the dipeptide carrier.
The selection of the dipeptide carrier must take in
account the potential side-effects of the corresponding
DKP formed during the cyclization.
s), 4.45 (1H, m), 7.02 (2H, d, J = 9.0 Hz), 7.62 (2H, d,
J = 8.7 Hz), 8.17 (3H, s), 8.88 (1H, d, J = 7.5 Hz), 10.10
1
3
(
1H, s); C NMR ((CD ) SO, 75 MHz): d 18.01, 18.86,
3 2
2
1
3
3.82, 29.93, 57.69, 64.85, 119.89, 121.56, 137.21, 145.17,
66.62, 168.26, 170.04; MW (Da): 307.2231 (calcd,
07.3451).
1
2. General procedure for the monitoring of drug release by
HPLC: A solution of the compound to be assayed
ꢀ4
(
10 M) in aqueous buffer (pH 7.4) was kept at a constant
Acknowledgements
temperature of 37.0 ± 0.1 ꢀC; aliquots were periodically
taken and immediately injected (loop of 100 lL) in the
HPLC system, using a LichroCart 250-4 Lichrospher 100
RP-8 reverse phase column (250 · 4 mm, 5 lm); the
CRS thanks Funda c¸ a˜ o para a Ci eˆ ncia e Tecnologia
FCT, Portugal) for Ph.D. grant SFRH/BD/9272/2002.
PG and RM thank FCT and FEDER for financial sup-
port to CIQUP and CECF, respectively.
(
elution was isocratic, at varying proportions of CH CN
3
in aqueous buffer (sodium hexanesulfonate 10 mM,
sodium acetate 2.5 mM, phosphoric acid 2.5 mM;
pH 6.3) and at a flow rate of 1.0 mL/min, with detection
at 240 nm; paracetamol and the relevant DKPs were used
as standards for peak identification; to exemplify, the
monitoring of drug release from compound 4i was carried
References and notes
1
2
. Friis, G. J.; Bundgaard, H. In A Textbook of Drug Design
and Development; Krogsgaard-Larsen, P., Liljefors, T.,
Madsen, U., Eds., 2nd ed.; Harwood Academic: Amster-
dam, 1996; p 351.
out using 8% CH CN in aqueous buffer as HPLC solvent,
3
and retention times for the relevant DKP, paracetamol
and 4i were 9.90, 7.70 and 4.10 min, respectively.
13. Purdie, J. E.; Benoiton, N. L. J. Chem. Soc., Perkin Trans.
2 1973, 13, 1845.
˚
14. Meresaar, U.; Agren, A. Acta Pharm. Suec. 1968, 5, 85.
. Boyer, T. D.; Rouff, S. L. J. Am. Med. Assoc. 1971, 218,
440.
3
4
. Dahlin, D. C.; Nelson, S. D. J. Med. Chem. 1982, 25, 885.
. Vermeulen, N. P.; Bessems, J. G.; Van de Straat, R. Drug
Metab. Rev. 1992, 24, 367.
15. Jensen, E.; Bundgaard, H. Int. J. Pharm. 1991, 71, 117.
16. Larsen, S. W.; Ankersen, M.; Larsen, C. Eur. J. Pharm.
Sci. 2004, 22, 399.
5
6
7
8
9
. Bousquet, E.; Marrazzo, A.; Puglisi, G.; Spadaro, A.;
Tirendi, S. J. Pharm. Pharmacol. 1996, 48, 479.
. Kovach, I. M.; Pitman, I. H.; Higuchi, T. J. Pharm. Sci.
17. Craig, P. N. In Comprehensive Medicinal Chemistry;
Hansch, C., Ed.; Pergamon: Oxford, 1990; Vol. 6, p 245.
18. Charton m values taken from Exner, O. In Correlation
Analysis in Chemistry; Chapman, N. B., Shorter, J., Eds.;
Plenum: New York, 1978; p 439.
19. Lloyd-Williams, P.; Albericio, F.; Giralt, E. Chemical
Approaches to the Synthesis of Peptides and Proteins; CRC:
Boca Raton, 1997; p 60.
1
981, 70, 881.
. Goolcharran, C.; Borchardt, R. T. J. Pharm. Sci. 1998, 87,
83.
2
. Shan, D.; Nicolaou, M. G.; Borchardt, R. T.; Wang, B.
J. Pharm. Sci. 1997, 86, 765.
. Wipf, P.; Li, W. L.; Adeyeye, C. M.; Rusnak, J. M.; Lazo,
J. S. Bioorg. Med. Chem. 1996, 4, 1585.
20. The effect of compounds 4d, 4h, 4i and paracetamol on the
hepatic levels of glutathione was determined as follows:
healthy male BALB/c mice, 17–21 g and 5 weeks old, were
allowed free access to water and pelleted food; mice were
randomly divided into five groups of four animals each;
four groups were treated ip with a single dose of 3.3 mmol/
kg of paracetamol or ester 4 (in 30% of propyleneglycol);
the vehicle was administered ip to a control group; 2 h
post-administration, the animals were sacrificed and the
liver removed and kept on ice; glutathione in homogenized
1
1
0. Hamel, A. R.; Hubler, F.; Carrupt, A.; Wenger, R. M.;
Mutter, M. J. Pept. Res. 2004, 63, 147.
1. Spectroscopic data for compounds 5c and 4c (5c is a
synthetic precursor of 4c):
Compound 5c: H NMR ((CD
(
1
3
)
3H, d, J = 6.9 Hz), 1.10 (3H, d, J = 6.9 Hz), 2.04 (3H, s),
2
SO, 300 MHz): d 1.07
4
.18 (1H, d, J = 5.1 Hz), 7.11 (2H, d, J = 8.7 Hz), 7.64
C
1
3
(
NMR ((CD
2H, d, J = 8.7 Hz), 8.64 (3H, br s), 10.12 (1H, s);
0
)
2
SO, 75 MHz): d 17.65, 18.26, 23.86, 29.54,
7.35, 120.06, 121.50, 137.60, 144.64, 167.93, 168.42; MW
liver was immediately determined using 5,5 -dithiobis-(2-
3
5
nitrobenzoic acid) (DTNB) as described in Sedlak, J.;
Lindsay, R. H. Anal. Biochem. 1968, 25, 192.
21. Thomsen, K. F.; Bundgaard, H. Int. J. Pharm. 1993, 91,
39.
(
Compound 4c: H NMR ((CD
Da): 250.1935 (calcd, 250.2937).
1
3 2
) SO, 300 MHz): d 1.03
(
6H, d, J = 6.6 Hz), 2.04 (3H, s), 2.25 (1H, m), 3.71 (2H,